Also known as Ecology of Crime, Chain Reaction, Carnage, Twitch of the Death Nerve and Blood Bath, Last House on the Left – Part II and New House on the Left, this is the most violent and nihilistic of all of Mario Bava’s films. It started as a story idea so that Bava could work with Laura Betti (Hatchet for the Honeymoon) again, with the original titles of Stench of Flesh and Thus We Do Live to Be Evil, but had a virtual litany of writers get involved, including producer Giuseppe Zaccariello, Filippo Ottoni, Sergio Canevari, Dardano Sacchetti (who co-wrote all of Fulci’s best films, like Zombi 2 and House by the Cemetery) and Franco Barberi.

Bava was devoted to the film and its low budget meant that he would also be his own cinematographer, often creating innovative tracking shots with a toy wagon and relying on in-camera tricks to make it seem that the location was much more expansive than reality. 

There are thirteen murders in the film — many of which are incredibly gory thanks to the skill of Carlo Rambaldi — occur as several characters in the film vie to inherit the titular bay. The film divides critics and fans, who see it as pure gore versus the nuanced films that Bava is known for. For example, Christopher Lee went on record stating that he found the movie to be revolting.

It also gave rise to the slasher genre, as every film that follows owes it a debt of gory gratitude. And some owe it plenty more, in particular, Friday the 13th Part 2, which copies two of the kills in this film shot for shot.

The story is all over the place and has a mix of dark humor and pure meanness at its core, starting with Filippo Dontai strangling his wife, Countess Federica, before being stabbed and killed scant seconds later. His corpse is dragged to the bay, where his murder goes undiscovered as detectives begin their investigation into the death of the Countess.

That’s when we meet Frank (Chris Avram, Enter the Devil), a real estate agent, and his girlfriend Laura, who plot on taking over the bay. They were working with Donati to kill his wife and now need his signature, but don’t realize that he was killed.

Meanwhile, four teenagers hear about the murders and break into the mansion. One of them, Brunhilda, skinny dips in the bay until the dead corpse of Donati surfaces and touches her. She screams and runs toward the mansion, only to be killed by an unseen murderer holding a billhook. That killer uses that same weapon to kill her boyfriend, Bobby, then he impales Duke and Denise together with a spear while they’re having sex. Here’s a good lesson that I always yell: don’t fuck in the woods, don’t fuck in a haunted house, don’t fuck when a killer is about.

The killer ends up being the Countess’ illegitimate son, Simon, who is wiping everyone out under the orders of Frank. Renata (Claudine Auger, Thunderball) shows up to throw a wrench in the work, as she’s the Countess’ real daughter. Along with her husband Albert, she begins to make plans to kill her half-brother.

What follows is a near Grand Guignol of back and forth murder: Frank attacks Renata, who turns the tables and stabs him with a knife. Paolo, the entomologist who lives on the estate grounds, sees the killing but is strangled by Albert before he can call the police and his wife is decapitated with an axe. Laura shows up, but Simon strangles her to death before Albert kills him. Frank shows up again, but Albert takes him out, leaving Renata as the sole heir.

They return home to await being awarded the money, but as they get to the front door, their children shoot them with a shotgun, thinking they are playing with their parents. Bored with the game and how long their parents are playing dead, the kids run out to play another game in an ending that can either be viewed as pure comedy or a sad comment on humanity. Maybe both.

Bay of Blood isn’t the art of past Bava films, but it’s not trash. It’s also been claimed to have been Bava’s favorite film that he directed. And Dario Argento adores the movie so much that he literally stole a print of it from a theater!

You don’t have to resort to larceny. You can just watch this on Shudder.